An objective of radiation therapy is to maximize the amount of radiation to a target volume (e.g., a cancerous tumor) and minimize the amount of radiation to healthy tissues and critical structures. Verification of the location of the target volume prior to the administration of a dose of therapeutic radiation is key to the objective. Another objective is to minimize the amount of time to set up and administer the therapeutic radiation treatment. Typically, many clinics have to use linear accelerators for a considerable (e.g., 30-40 minutes) amount of time to start new patients with setup and treatment plan verification. Unfortunately, since care providers treat multiple patients and each patient is treated over 30 to 40 fractionated sessions, the time allowed for each session is relatively short, e.g. 10 to 15 minutes, so the process must be fast as well as accurate.
Radiotherapy simulator machines have traditionally been used to perform the pre-treatment analysis of the target volume before a radiotherapy treatment machine applies the therapeutic radiation. These radiotherapy simulators are a costly investment.
For example, among other components, a traditional radiotherapy simulator machine may use a bulky image intensifier tube detector and/or require time-consuming film processing to capture images of the target volume. Film processing includes questionable environmental, health, and safety issues. Furthermore, these image intensifier tube detectors have the disadvantage of being very large relative to their imaging area. They also have image spatial distortions from their spherical-shaped input surface and the orientation of the intensifier tube with the Earth's magnetic field.
One example of a simulator machine of the prior art is the Ximatron Simulator by Varian Medial Systems of Palo Alto, Calif. The Ximatron is limited by requiring treatment plans to be imported from another device (e.g., a CT scanner) for verification (e.g., verification of dose plans for irregular fields). Furthermore, if the treatment plan requires any adjustments based on the verification, the treatment plan must first be updated on the other device, and then the updated treatment plan must be imported back into the Ximatron for another verification. This prior art process would repeat if the verification requires further corrections. Therefore, this prior art process is very time-consuming and costly.
Another prior art device is the Helax simulator made by MDS Nordion. The Helax device provides for field shapes to be projected onto the skin of a patient for marking by means of a liquid-crystal display (“LCD”) projection panel. The LCD panel is a separate component from the simulator and thus the LCD display must be fitted onto the outside of the head of the simulator. One problem with this arrangement is that the projected image is difficult to see. Furthermore, the LCD projection of the Helax simulator only projects one image onto a patient at a time.